This invention relates to a flat plate dialyzer and method of making same and more particularly to a compact hemodialysis unit having a small volumetric capacity and minimum pressure resistance to blood flow therethrough which can be used without the need for blood transfusion and/or blood pumps.
A common type of hemodialysis unit consists of tightly wound coil of permeable membrane tubing submerged in dialysate. Since the tubing is long and tightly wound, considerable back pressure is developed within the unit and a blood pump is required to force blood through the tubing. In addition, the blood inventory in the coiled tubing is substantial and a transfusion often is required when the machine is used. Since only a small part of the transfused blood which is used to prime a coil can be recovered, this represents added expense and inconvenience to a person undergoing hemodialysis. In light of these problems with dialyzer coils, flat plate dialyzers have become popular for use in treatment of kidney diseases.
Many flat plate dialyzers disclosed in the prior art consist of alternating layers of permeable membrane tubing and support material which are sealed on the ends with an epoxy resin or similar sealing material and installed in a casing. One of the problems in configurations like this, however, is the difficulty in opening up a flow through the permeable membrane tubing, the walls of which tend to stick together during the manufacturing process. Another problem is pulling or peeling of sealing material from the permeable membrane tubing which introduces leakage between the blood and dialysate flow paths.
One approach to the problem of opening up membrane tubing in a flat plate dialyzer is illustrated in Lavender et al U.S. Pat. No. 3,522,885 issued Aug. 4, 1970. This patent discloses inserts placed within the membrane tubing during manufacture which are removed after manufacture is completed. The use of such inserts, however, has many obvious drawbacks such as the extra labor needed to insert and remove the inserts as well as the increased possiblity of tearing or otherwise penetrating the delicate membrane tubing. Another approach to the problem of keeping the tubing open after manufacture is illustated in Lavender U.S. Pat. No. 3,565,258 which discloses support material such as non-woven mesh inserted in the tubes. However, this has the same drawbacks as the approach in the U.S. Pat. No. 3,522,885 to Lavender, i.e. tearing of the tube and cost of labor needed to insert the mesh in the tube. The Lavender U.S. Pat. No. 3,565,258 also has the disadvantage of requiring very careful application of sealing material between each layer of tubing which can substantially increase the cost of the device.